Sleeper’s Hill Hampshire

Sleeper’s Hill, is a development site on George Eyston Drive in Winchester, Hampshire. The drive was named after Captain George Edward Thomas Eyston MC OBE (28 June 1897 – 11 June 1979) who was a British racing driver in the 1920s and 1930s, and he broke the land speed record three times between 1937 and 1939.[1]

George Eyston was also an engineer and inventor… An auspicious character to follow!
Sited on a private road of exclusive, individual homes, achieving planning permission on this mature and established plot needed thoughtful planning and sensitive design.

Alfred Homes, the developers, contacted Technical Arboriculture Ltd in Spring 2014 and an initial tree report and tree constraints document has aided and directed the achievable development layout for Alfred Homes which maximises the plot placement for each individual home, whilst still incorporating a number of valued and important trees and a beautiful dual beech avenue subject to a TPO along the northern boundary. Alfred Homes were also keen to use the naturally occurring screening provided on an established plot like this to enhance the exclusive nature of the development.

Understanding and balancing the needs of the site, the environment and planning, the neighbours and the prospective homeowners is tricky. Homeowners want south facing gardens with light into the main reception rooms, patios outside garden doors, bathed in the sun until dusk. Neighbours want noise protection, screening and minimal disturbance. Developers want to create a stunning, desirable and economical build. And all the while the environment and existing planting most likely just want it to stay exactly where it is!

On this development the ideal development access point was where the dual beech avenue (subject to a TPO) hugged the northern perimeter. Placing access to new homes when multiple houses are built onto one initial plot can be difficult but without access there are no plots, there is no building and there can be no development.
So how did Technical Arboriculture help? Primarily through low impact surfacing. As an experienced Arboriculturist, Kevin Cloud from Technical Arboriculture was happy to assist with guidance from the initial stages, through to still regularly visiting the site during the ongoing build phase. Whilst there were a number of technical aspects to this build which required the knowledge and input of an Arboriculturalist to achieve planning, the fundamental issue we look at here is the access road.

The Sleepers Hill Site had, as is normal, a previous entry point midway across the plot boundary to a centrally located original house. This is not an ideal access point for multiple dwellings, some end up with north facing gardens, funny shaped plots and unfair distributions of established planting. Technical Arboriculture provided a tree report, which identified that access could be achieved across the northern perimeter of the plot, exactly where the stunning double avenue of Beech trees are. Through liaising with the Winchester City Council Tree Officer and assessing the condition and viability of the trees, a new access plan was drawn up requiring the removal of only two of the poorest quality beech trees from the dual Avenue. (shown with red crown spreads in the drawing below).

This is where the low impact surfacing comes in, designed to allow vehicular access on highways (or driveways) for up to 145kN/axle, which is more than the weight of a fully loaded fire engine or . Low impact surfacing allows the tree roots or Root Protection Area (RPA) to be overbuilt without compromising the trees ability to nourish and stabilise through its root system in line with BS5837.

But how?

Well, products like Cellweb (others brands do also exist) come on a roll approximately 20mm wide. A strip is rolled out the length required and the width is created by staking one side and unfolding like a concertina between the edging boards, creating a 3D grid structure straight onto a layer of geo-textile material pegged down with minimal removal of the surface mat only, in the case of Sleeper’s Hill, there was little top soil so as much as possible was kept as the site substructure is very chalky. The cells or pockets created from the grid material are filled with angular stone aggregate.

Why angular stone aggregate?

Because it interlocks with the sharp edges making it stable whilst retaining a porous nature allowing rain water to permeate the ground and gaseous exchange to occur, allowing the tree roots to breathe and encouraging healthy and prolonged growth. The shape of the pockets mean the forces from vehicles are distributed outwards into neighbouring cells preventing dipping and sinking and significantly reduces compaction under heavy weight vehicles.

Edging boards to support the sides of the low impact surfacing.

Low impact Surfacing Expanded between supporting edges

In this example (below) you can see how the layers go down, edging boards, geo-textile, low impact surfacing, aggregate, then a top layer. For the period when the homes are being built and additional access is required by construction vehicle and contractors, a temporary layer of asphalt is put down – this will be removed at the end of the build phase and replaced with a permeable and aesthetic top dressing.

Image showing the layers of aggregate

Again, in the photograph above, on the left hand side you can see that the area to the left of the edging boards is being prepared too, this will be temporary parking for the contractors working on site, reducing the impact on the neighbours and the cars parked around the site on neighbouring roads. When the development is complete the Cellweb and surfacing is lifted and the area to the left of the drive will be planted with young Beech trees to provide future preservation of the beech avenue and visual screening.
We look forward to updating you when the build completes.